In‐depth analysis of InAlN/GaN HEMT heterostructure after annealing using angle‐resolved X‐ray photoelectron spectroscopy

Abstract

During high-electron-mobility transistor elaboration process, a thermal treatment of In 0.2 Al 0.8 N (InAlN) barrier layer is performed in order to improve electrical performances. We showed previously that In 0.2 Al 0.8 N/GaN heterostructures, annealed at 850 C under O 2 partial pressure, present a specific in-depth organization. Angleresolved X-ray photoelectron spectroscopy is a powerful tool to precisely determine the spatial localization and relative position of the different interfaces, from InAlN until buried GaN layer. The proposed in-depth model of the stack evidences (1) an Al-rich surface oxide with embedded N 2 molecules, (2) an interlayer of InAlN <1 governed by nitrogen lattice defects, (3) a stable In 0.2 Al 0.8 N matrix, and finally (4) the GaN buffer layer underneath.

Oxidation Behavior of InAlN during Rapid Thermal Annealing

“…The decrease in the N concentration at the top of the remaining InAlN layer (see Figure 3b) suggests the formation of N vacancies within the Wurtzite structure, which is consistent with previous X-ray photoelectron spectroscopy studies. [12,30] The presence of N vacancies below the original InAlN surface likely causes a reduction in the spontaneous polarization within the Wurtzite structure. [31] Eickelkamp and coworkers showed that annealing of a 12 nm-thick InAlN film for 2 min at 800 C degrades the carrier concentration and mobility in the 2DEG at the InAlN/GaN interface.…”